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Task/Sorting-algorithms-Permutation-sort/Scheme/sorting-algorithms-permutation-sort.ss

@@ -0,0 +1,25 @@
+(define (insertions e list)
+  (if (null? list)
+      (cons (cons e list) list)
+      (cons (cons e list)
+            (map (lambda (tail) (cons (car list) tail))
+                 (insertions e (cdr list))))))
+
+(define (permutations list)
+  (if (null? list)
+      (cons list list)
+      (apply append (map (lambda (permutation)
+                           (insertions (car list) permutation))
+                         (permutations (cdr list))))))
+
+(define (sorted? list)
+  (cond ((null? list) #t)
+        ((null? (cdr list)) #t)
+        ((<= (car list) (cadr list)) (sorted? (cdr list)))
+        (else #f)))
+
+(define (permutation-sort list)
+  (let loop ((permutations (permutations list)))
+    (if (sorted? (car permutations))
+        (car permutations)
+        (loop (cdr permutations)))))